Thursday, January 28, 2010

GRIZZLY OR BROWN BEAR?

This series of photos is intended to demonstrate just how variable the brown bear is in a single population - all of these bears were photographed last year in early August along the Katmai coast. A young adult brown bear is shown above (sex unknown). Photo by Scott W. Michael.

Ursus arctos is one of the most revered and feared beasts on earth. This mammal has been given numerous appellations, including grizzly, brown, coastal brown, Alaska brown and Kodiak bear. As a neophyte to bear classification, I found myself very confused by the common vernacular, as well as the scientific nomenclature applied to this bruin. How many species or subspecies are there and do these common names represent disparate populations?

Queenie, an elderly sow. Photo by Scott W. Michael.

It turns out that all of these common names refer to a single species - Ursus arctos. Typically, the term brown bear (as well as coastal and Alaskan brown bear) is applied to U. arctos populations that live in coastal Alaska, while Kodiak bear is used for “brownie” populations that live in the Kodiak Island archipelago (this includes the islands of Kodiak, Afognak, and Shuyak). Grizzly is usually reserved for U. arctos populations in the interior of Alaska, in Canada and the lower 48 states. While you can call them whatever common name you wish, they are all Ursus arctos.

An adult female known as Ms. Hook (she had two spring cubs at this time). Photo by Scott W. Michael.

OK - HOW MANY SUBSPECIES?

So they all fall under the single binomial Ursus arctos - but are brown and grizzly bears different enough to warrant distinct subspecies status? And how about the Kodiak bear – doesn’t it represent a different subspecies? (OK, I know many of you are starting to suffer from brain fog because of taxonomic overload, but I enjoy this stuff, so bear with me!)

Traditionally, subspecies have been defined as populations that differ slightly from one another, but that are not disparate enough to be elevated to the level of distinct species. In most cases, a subspecies represents a group of individuals that has been isolated from the main population long enough to exhibit some degree of change, but yet if they breed with members of the original population they will still produce viable offspring.

There has been much debate about how many subspecies of U. arctos actually exist in North America. In the early twentieth century (1918 to be exact) it was proposed that there were 86 subspecies of U. arctos in North America alone! This classification scheme was soon shot to pieces by the taxonomically-inclined, leading bruin biologists to recognize only two subspecies: the mainland populations, which were recognized as Ursus arctos horribilis, and the bear population of the Kodiak Island archipelago, which were referred to as U. a. middendorffi.

A young adult male. Photo by Scott W. Michael.

So, everything appeared to be as clear as mud until DNA analysis came on the scene. DNA has a biochemical signature that enables scientists to distinguish species and study their degree of relatedness. Recently, using mitochondrial DNA, researchers struck a body blow to the widely accepted North American-Ursus arctos classification scheme. These molecular surveys indicate that there is actually only one subspecies of brown bear in all of North America – this subspecies should be called Ursus arctos arctos (no more horribilis or middendorffi).

Adult boar named Mickey. Photo by Scott W. Michael.

In a nutshell, this means that the grizzly bear, Kodiak bear and brown bear are all the same beast. It is a wide-ranging subspecies that does not only roam throughout North America, it is also found over much of Eurasia as well. That’s right, U. arctos arctos is a circum-global species, having been reported from the Balkans, Caucasus, Carpathians, Pyrenees, Italy (Abruzzo and the Benta Mountains), the Baltic States, Scandinavia (excluding Denmark), Greece, Syria, Russia and the countries of the Tibetan plateau (China, Tibet and Nepal). That said, there are a number of other valid subspecies on the European and Asian continents. (A side note: another very odd conclusion the molecule purveyors came to is that certain populations of brown bears are more closely related to the polar bear [Ursus maritimus] then they are to other brown bears! Now my head hurts!)

A large boar (in his prime) dubbed Pythagoras. Photo by Scott W. Michael.

AMAZING VARIABILITY

While it may be that brown and grizzly bears are not distinct on the molecular level, some bear buffs still insist that the inland grizzly and coastal brown bears are different animals. There is no doubt, that some individuals from coastal regions do not look like their inland kin. A male coastal brown bear often has a more elongated neck, longer legs, and more protuberant face than its landlocked “cousin,” while inland boars are often more compact, with a shorter neck, shorter appendages and more concave face. But when it comes to physical appearances, there are no hard fast rules that can be consistently used to separate the coastal and inland populations.

This incredible variability in U. arctos populations is acutely demonstrated by the studies of Dr. Ian Sterling and Andrew DeRocher. These researchers examined a set of male U. arctos skulls from the Caucus Mountains, Russia. They noted that while some skulls looked like those of a “classic” brown bear, there was also a skull that resembled a panda (with short face and high profile) and another that looked more like a wolf cranium (i.e., it was more elongate and slender)!

Above, I mentioned that in 1918, a researcher described 86 different “species” of brown and grizzly bears in North America. Most of his research was based on the examination of skulls at the National Museum (sometimes only a single specimen of a particular “species”). Another researcher came-up with an even more elaborate classification scheme – he concluded that the skeletons of extinct and modern day brown bears he examined represented 232 distinct ursid species. In actual fact they all belonged to the highly variable U. arctos!

Although sporting some nicks and cuts, this boar is in his prime - this is Tank. Scott W. Michael.

You only have to look at the photos of the brown bears in this blog (I have included a number of shots above) to see that most grizzlies do not look exactly alike. In fact, individuals are often so unique in appearance that bear-viewers regularly name them and readily recognize them from one year to the next. Some individuals have big ears; in others the ears are relatively petite. The bodies of some are long and lanky, while those of others are short and squat. Some have a long, prominent snout; others have the “classic” grizzly “dish” (concave) face. Some of these characteristics also change from spring to fall (e.g., bears get girthy as they pile on weight for the winter) and as the bears age (e.g., subadult males tend to be more gracile and finely built than males in their prime). The color of the pelage is not a constant either -there are blond, brunette, black furred and, on rare occasions, even white brown bears! In conclusion, while there may be differences between some individuals in coastal and inland population, you cannot consistently distinguish between the different populations.

About Me

I am into animals (especially those that live in marine environs, grizzly bears and dogs) and have been blessed to be able to make a living sharing my love with others. I have written 11 books on sharks, rays, coral reef fishes and marine invertebrates and have had thousands of photos published worldwide in books, magazines and on the internet. I am currently writing for a number of aquarium publications.